1. Field
Embodiments of the present invention relate to a coolant-control valve that controls the flow of coolant of an engine.
2. Description of Related Art
In an engine (internal combustion engine) of a vehicle such as an automobile, a technique has been studied in which, for the purpose of improvement in warming-up performance of the engine and improvement in fuel efficiency due to operation of the engine at an optimum temperature, apart from a main flow passage that circulates the coolant between the engine and a radiator, a bypass flow passage configured to directly return the coolant to the engine by bypassing the radiator is provided, and a coolant-control valve is provided in the main flow passage to adjust a degree of opening of the coolant-control valve depending on a coolant temperature and other values, thereby controlling an amount of coolant that flows through the main flow passage and is cooled by the radiator. In addition, the coolant is circulated by a pump that is driven by the engine. During operation of the engine, and when the coolant-control valve is open, the coolant mainly circulates in the main flow passage, and when the coolant-control valve is closed, the coolant circulates in the bypass flow passage.
For example, when starting up the engine in which the coolant temperature is low, the coolant is directly returned to the engine from the bypass flow passage without passing through the radiator by blocking the main flow passage, thereby promoting the warming-up of the engine. Furthermore, for example, in order to control the temperature of the coolant to optimize the combustion of fuel in the engine even after warming-up, opening and closing (degree of opening) of the coolant-control valve is adjusted.
In such a coolant-control valve, the use of a rotary type valve or the like has been studied.
In the rotary type valve, for example, a flow passage is provided in the rotor, and an opening portion is formed in a housing that houses the rotor. The opening portion is connected to an external flow passage, and communicates with the flow passage in the rotor in the case of an angle in which an angle of the rotor is open. The coolant-control valve is open and closed by a rotational angle of the rotor, and the degree of opening is adjusted to adjust the flow rate.
Thus, for example, during assembly of the coolant-control valve, at the time of start of operation of the coolant-control valve after completion, there is a need for initialization learning of angle of a fully-closed position and a fully-open position. For example, a technique has been suggested in which, in a cooling system controller of an engine that adjusts engine water temperature, with respect to a thermo valve, a heater valve, and an oil valve, the initial process of changing the valve from a fully-open state to a fully-closed state is performed at the time of start of electric conduction (for example, refer to Patent Literature 1).
Furthermore, although it does not relate to the initialization learning, for example, a technique has been suggested in which, in a flow rate control valve for controlling the engine coolant, the valve opening is restricted by a mechanical stopper to prevent an occurrence of inconvenience of a valve at the time of malfunction or the like (for example, refer to Patent Literature 2).
3. Patent Literature
Patent Literature 1: Japanese Publication No. 2007-23989 W
Patent Literature 2: Japanese Publication No. 2002-98245 W